SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Function if (children 1)
     ExpressionList (children 3)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier index_length
        Literal UInt64_0
      Literal \'OK\'
      Literal \'FAIL\'
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier information_schema.tables
   Function and (children 1)
    ExpressionList (children 2)
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier table_name
       Literal \'tables\'
     Function equals (children 1)
      ExpressionList (children 2)
       Identifier table_schema
       Literal \'system\'
